Process for preparing polymers of C2-C10 alkenes in the presence of metallocene complexes with cationically functionalized cyclopentadienyl ligands

ABSTRACT

Polymers of C 2 -C 10  alkenes are prepared in the presence of catalyst systems comprising as active constituents 
     A) a metallocene complex of the general formula I                    
      where the substituents and indices have the following meanings: 
     M is titanium, zirconium, hafnium, vanadium, niobium or tantalum, 
     R 1  to R 4  are hydrogen, C 1 -C 10 -alkyl, 5- to 7-membered cycloalkyl which in turn can bear a C 1 -C 10 -alkyl as substituent, C 6 -C 15 -aryl or arylalkyl, where two adjacent radicals may also together be cyclic groups having from 4 to 15 carbon atoms, Si(R 6 ) 3 ,                    
      where 
     R 6  is C 1 -C 10 -alkyl, C 6 -C 15 -aryl or C 3 -C 10 -cycloalkyl, 
     R 7  and R 8  are hydrogen, C 1 -C 10 -alkyl, C 6 -C 15 -aryl or C 3 -C 10 -cycloalkyl, 
     R 9  and R 10  are C 1 -C 10 -alkyl, C 6 -C 15 -aryl or C 3 -C 10 -cycloalkyl, 
     Y is nitrogen, phosphorus, arsenic, antimony, or bismuth, 
     Z is oxygen, sulfur, selenium or tellurium, 
     n is an integer in the range from 0 to 10,                    
     B) a compound forming metallocenium ions.

Preparation of polymers of C₂-C₁₀-alkenes in the presence of metallocenecomplexes having cationically functionalized cyclopentadienyl ligands

The present invention relates to a process for preparing polymers ofC₂-C₁₀-alkenes in the presence of catalyst systems.

The present invention further provides for the use of the polymersobtainable in this way for producing fibers, films or moldings as wellas the fibers, films and moldings obtainable therefrom.

The metallocenes used for the polymerization of alkenes are generallyvery sensitive to air and moisture, which makes the use of thesemetallocenes difficult since they have to be handled under an inert gasatmosphere.

EP-A 608 054 describes catalyst systems for preparing polyolefins, inwhich the metallocene complexes are functionalized with Lewis bases.These complexes are very sensitive to air and moisture.

The same disadvantage is exhibited by the catalyst systems described inOrganometallics 1994, 13, 4140-4142 for preparing polyethylene andpolypropylene, these likewise comprising metallocene complexesfunctionalized with Lewis bases.

It is an object of the present invention to provide metallocene catalystsystems for polymerizing alkenes, which catalyst systems are insensitiveto air and moisture and thus are simpler to handle.

We have found that this object is achieved by a process for preparingpolymers of C₂-C₁₀-alkenes in the presence of catalyst systemscomprising as active constituents

A) a metallocene complex of the general formula I

 where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium or tantalum,

R¹ to R⁴ are hydrogen, C₁-C₁₀-alkyl, 5- to 7-membered cycloalkyl whichin turn can bear a C₁-C₁₀-alkyl as substituent, C₆-C₁₅-aryl orarylalkyl, where two adjacent radicals may also together be cyclicgroups having from 4 to 15 carbon atoms, Si(R⁶)₃,

 where

R⁶ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

R⁷ and R⁸ are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

R⁹ and R¹⁰ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

Y is nitrogen, phosphorus, arsenic, antimony, or bismuth,

Z is oxygen, sulfur, selenium or tellurium,

n is an integer in the range from 0 to 10,

 where

R¹¹ and R¹² are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl orC₃-C₁₀-cycloalkyl,

R¹³ and R¹⁴ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

n¹ is an integer in the range from 0 to 10,

X¹ to X⁴ are fluorine, chlorine, bromine, iodine, hydrogen,C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms inthe alkyl radical and from 6 to 20 carbon atoms in the aryl radical,—OR¹⁵, —NR¹⁵ R¹⁶ or

 where

R¹⁵ and R¹⁶ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl,fluoroalkyl or fluoroaryl, each having from 1 to 10 carbon atoms in thealkyl radical and from 6 to 20 carbon atoms in the aryl radical,

R¹⁷ to R²¹ are hydrogen, C₁-C₁₀-alkyl, 5- to 7-membered cycloalkyl whichin turn can bear a C₁-C₁₀-alkyl as substituent, C₆-C₁₅-aryl orarylalkyl, where two adjacent radicals may also together be cyclicgroups having from 4 to 15 carbon atoms, Si(R²²)₃,

 where

R²² is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

R²³ and R²⁴ are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl orC₃-C₁₀-cycloalkyl,

R²⁵ and R²⁶ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

n² is an integer in the range from 0 to 10 and

o, p, q, r are integers in the range from 0 to 4, where the sumo+p+q+r+1 corresponds to the valence of M and

B) a compound forming metallocenium ions.

Furthermore, the present invention provides for the use of the polymersobtainable in this way for producing fibers, films or moldings andprovides the fibers, films and moldings obtainable therefrom.

Among the metallocene complexes of the general formula I which are usedin the process of the present invention, preference is given to those inwhich

M is titanium, zirconium or hafnium, in particular titanium,

R¹ to R⁴ are hydrogen, C₁-C₆-alkyl, C₆-C₁₅-aryl or where two adjacentradicals may be cyclic groups having from 8 to 12 carbon atoms, inparticular hydrogen,

 where

R¹¹ and R¹² are hydrogen or C₁-C₄-alkyl, in particular hydrogen, methylor ethyl,

R¹³ and R¹⁴ are C₁-C₆-alkyl, in particular methyl, ethyl, n-propyl,iso-propyl, n-butyl or tert.-butyl or phenyl,

n¹ is an integer in the range from 1 to 4,

Y is nitrogen or phosphorus,

Z is oxygen or sulfur,

X¹ to X⁴ are chlorine, C₁-C₄-alkyl or

 where

R¹⁷ to R²¹ are hydrogen, C₁-C₆-alkyl, C₆-C₁₅-aryl or where two adjacentradicals may be cyclic groups having from 8 to 12 carbon atoms or

R²³ and R²⁴ are hydrogen or C₁-C₄-alkyl, in particular hydrogen, methylor ethyl,

R²⁵ and R²⁶ are C₁-C₆-alkyl, in particular methyl, ethyl, n-propyl,iso-propyl, n-butyl or tert.-butyl or phenyl and

n² is an integer in the range from 1 to 4.

Particular preference is given to metallocene complexes of the generalformula I in which R⁵ is

in particular

and R¹ to R⁴ are hydrogen. It is also preferred, particularly when M istitanium, that X¹, X² and X³ are chlorine and o is 1, p is 1, q is 1 andr is 0 or that X¹ and X² are chlorine and X³ is

and o is 1, p is 1, q is 1 and r is 0, so that symmetrical complexesresult.

Examples of particularly preferred metallocene complexes of the generalformula I are:

trichloro-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]titanium(IV)chloride

dichlorodi-{η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]}titanium(IV)dichloride

trichloro-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]zirconium(IV)chloride

dichlorodi-{η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]}zirconium(IV)dichloride

trichloro-η⁵-[2-(N,N-dimethylammonium)ethylcyclopentadienyl]titanium(IV)chloride

dichlorodi-{η⁵-[2-(N,N-dimethylammonium)ethylcyclopentadienyl]}titanium(IV)dichloride

trichloro-η⁵-[2-(N,N-dimethylammonium)ethylcyclopentadienyl]zirconium(IV)chloride

dichlorodi-{η⁵-[2-N,N-dimethylammonium)ethylcyclopentadienyl]}zirconium(IV)dichloride

dichloro-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl](trimethylsilylcyclopentadienyl)titanium(IV)chloride

dichloro-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl](trimethylsilylcyclopentadienyl)zirconium(IV)chloride

dichloro-cyclopentadienyl-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]titanium(IV)chloride

dichloro-cyclopentadienyl-η⁵-[2-(N,N-diisopropylammonium)ethylcyclopentadienyl]zirconium(IV)chloride.

It is also possible to use mixtures of various metallocene complexes I.

The metallocene complexes I can be prepared by first preparing thecyclopentadienyl systems functionalized with the hetero atom by reactingcyclopentadienyllithium or cyclopentadienylsodium with a heteroatom-functionalized chloroalkane, as described in Journal ofOrganometallic Chemistry, 1992, 423, 31-38 and Journal of OrganometallicChemistry, 1994, 480, C18-C19. The hetero atom-functionalizedcyclopentadienyl systems can subsequently be reacted with alkyllithium,for example n-butyllithium to give the corresponding heteroatom-functionalized cyclopentadienyllithium systems, as described, forexample, in Journal of Organometallic Chemistry, 1995, 486, 287-289.These can now, preferably using MCl₄, be converted into thecorresponding metallocene complexes as described in Journal ofOrganometallic Chemistry, 1995, 486, 287-289, but with the metallocenecomplexes not yet bearing cationically functionalizedcyclopentadienylligands. The conversion to the metallocene complexes ofthe general formula I can be carried out by addition of acids of anytype, as described in Journal of Organometallic Chemistry, 1995, 486,287-289.

The addition of these acids gives a counterion to the metallocenecomplexes of the general formula I, this being derived from the acidadded. These counterions can be, for example: halides, carboxylateanions, sulfates, phosphates, carbonates, nitrates, PF₆ ⁻, BF₄ ⁻ or HPO₄²⁻. The type of counterion is not critical. Preference is given tohalides, in particular chlorides.

Suitable compounds B) forming metallocenium ions are, in particular,strong, neutral Lewis acids, ionic compounds containing Lewis-acidcations, ionic compounds having Bronsted acids as cation and aluminoxanecompounds.

As strong, neutral, Lewis acids, preference is given to compounds of thegeneral Formula IV

M¹X⁵X⁶X⁷  IV

where

M¹ is an element of main group III of the Periodic Table, in particularB, Al or Ga, preferably B,

X⁵, X⁶ and X⁷ are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl,arylalkyl, haloalkyl or haloaryl, each having from 1 to 10 carbon atomsin the alkyl radical and from 6 to 20 carbon atoms in the aryl radical,or fluorine, chlorine, bromine or iodine, in particular haloaryl,preferably pentafluorophenyl.

Particular preference is given to compounds of the general formula IV,in which X⁵, X⁶ and X⁷ are identical, preferablytris(pentafluorophenyl)borane.

Suitable ionic compounds containing Lewis-acid cations are compounds ofthe general formula V

[(A^(a+))Q₁Q₂ . . . Q_(z)]^(d+)  V

where

A is an element of main groups I to VI or transition groups I to VIII ofthe Periodic Table,

Q₁ to Q_(z) are radicals bearing a single negative charge, for exampleC₁-C₂₈-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl,each of which have from 6 to 20 carbon atoms in the aryl radical andfrom 1 to 28 carbon atoms in the alkyl radical, C₁-C₁₀-cycloalkyl whichmay be substituted by C₁-C₁₀-alkylgroups, halogen, C₁-C₂₈-alkoxy,C₆-C₁₅-aryloxy, silyl or mercaptyl groups,

a is an integer from 1 to 6,

z is an integer from 0 to 5,

d corresponds to the difference a-z, but with d being greater than orequal to 1.

Particularly suitable are carbonium cations, oxonium cations andsulfonium cations and also cationic transition metal complexes.Particularly useful examples are the triphenylmethyl cation, the silvercation and the 1,1′-dimethylferrocenyl cation. They preferably havenon-coordinating counter ions, in particular boron compounds as are alsomentioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.

Ionic compounds having Br6nsted acids as cations and preferably likewisenon-coordinating counterions are mentioned in WO 91/09882, the preferredcation being N,N-dimethylanilinium.

Particularly suitable as compound B) forming metallocenium ions areopen-chain or cyclic aluminoxane compounds of the general formula II orIII

where R²⁷ is a C₁-C₄-alkyl group, preferably a methyl or ethyl group,and

m is an integer from 5 to 30, preferably from 10 to 25.

These oligomeric aluminoxane compounds are usually prepared by reactinga solution of trialkylaluminum with water and is described, inter alia,in EP-A 284 708 and U.S. Pat. No. 4,794,096.

In general, the oligomeric aluminoxane compounds thus obtained aremixtures of chain molecules of various lengths, both linear and cyclic,so that m is to be regarded as a mean value. The aluminoxane compoundscan also be in the form of a mixture with other metal alkyls, preferablyaluminum alkyls.

Furthermore, it is also possible to use aryloxyaluminoxanes, asdescribed in U.S. Pat. No. 5,391,793, aminoaluminoxanes as described inU.S. Pat. No. 5,371,260, aminoaluminoxane hydrochlorides, as describedin EP-A 633 264, siloxyaluminoxanes, as described in EP-A 621 279 ormixtures thereof as component B).

It has been found to be advantageous to use the metallocene complexesand the oligomeric aluminoxane compound in amounts such that the atomicratio between aluminum from the oligomeric aluminoxane compound and thetransition metal from the metallocene complexes is in the range from10:1 to 10⁶:1, in particular in the range from 10:1 to 10⁴:1.

Solvents used for these catalyst systems are usually aromatichydrocarbons, preferably having from 6 to 20 carbon atoms, in particularxylenes and toluene and their mixtures.

The catalyst systems can also be used in supported form.

Support materials used are preferably finely divided supports whichpreferably have a particle diameter in the range from 1 to 300 μm, inparticular from 30 to 70 μm. Suitable support materials are, forexample, silica gels, preferably those of the formula SiO₂·a Al₂O₃,where a is a number in the range from 0 to 2, preferably from 0 to 0.5;these are thus aluminosilicates or silicon dioxide. Such products arecommercially available, e.g. silica gel 332 from Grace. Further supportsare, inter alia, finely divided polyolefins, for example finely dividedpolypropylene or magnesium chloride.

The process of the present invention can be carried out in the gasphase, in suspension, in solution and in liquid monomers. Suitablesuspension media are, for example, aliphatic hydrocarbons. The processof the present invention is preferably carried out in solution,preferably in toluene as solvent.

It has here been found to be particularly advantageous for themetallocene complex of the general formula I (with its counterion) to besuspended in toluene at from −80 to 110° C. and for the compound formingmetallocenium ions, likewise preferably as a toluene solution, to beadded at a pressure of from 0.5 to 50 bar. The actual polymerizationconditions are not critical per se; preference is given to temperaturesin the range from −50 to 300° C., pressures in the range from 0.5 to3000 bar and reaction times of from 0.1 to 24 hours. The polymerizationcan be stopped by addition of, for example, a methanolic/aqueoussolution of HCl.

The mean molecular weight of the polymers formed can be controlled usingthe methods customary in polymerization technology, for example byfeeding in regulators such as hydrogen.

Suitable C₂-C₁₀-alkenes for use in the polymerization are, inparticular, ethylene, but also propylene or higher alk-1-enes such asbut-1-ene, pent-1-ene and hex-1-ene. For the purposes of the presentinvention, polymers may be either homopolymers or copolymers.

The polymers prepared by the process of the present invention can bereadily processed and are suitable for producing fibers, films andmoldings.

The process of the present invention is particularly notable for thefact that the metallocene complexes used are insensitive to air andmoisture and can therefore be handled readily.

EXAMPLES Examples 1 to 3

Preparation of the Metallocene Complexes I

Example 1

Preparation of

A solution of 7.65 mmol of

in 40 ml of ether (prepared from 1.48 g (7.65 mmol) of

and 4.78 ml(7.65 mmol) of a 1.6 molar n-butyllithium solution in diethylether) was added dropwise at −30° C. to a solution of 1.45 g (7.65 mmol)of TiCl₄ in 70 ml of toluene. The reaction mixture was subsequentlyallowed to warm up to room temperature over a period of 2 hours and wasstirred for a further 14 hours. The solution was filtered and thesolvent was taken off under reduced pressure. The product was obtainedin the form of a deep red oil. Yield: 1.70 g (64%).

¹H-NMR (CDCl₃):δ=0.91 (d, ³J=6.6 Hz, 12H, CH—CH ₃), 2.69 (t, ³J=7.4 Hz,2H, Cp—CH ₂), 2.88 (t, ³J=6.8 Hz, 2H, N—CH ₂), 2.99 (m, 2H, CH—CH₃),6.86, 6.89 (m, 4H, Cp—H).

500 mg (1.44 mmol) of this product were admixed with 15 ml ofHCl-saturated methanol solution and stirred for 30 minutes. Afterremoving the solvent under reduced pressure, the residue was washedtwice with 20 ml each time of pentane to give an orange-brown solid.Yield: 510 mg (1.34 mmol, 93%). Mp.: 130° C. (decomposition).

¹H-NMR (CD₃OD):δ=1.42, 1.44 (2d, ³J=4.8 Hz, 12H, CH—CH ₃), 3.24 (m, 2H,Cp—CH ₂), 3.47 (m, 2H, N—CH ₂), 3.80 (m, 2H, CH—CH₃), 6.61, 6.67 (m, 4H,Cp—H).

¹³C-NMR (CD₃OD): δ=17.2, 18.7 (CH—CH ₃), 29.2 (Cp—CH₂), 47.5 (CH₂—N),56.6 (CH—CH₃), 120.4, 121.2 (ring—CH═), 133.7 (ring═C—CH₂—CH₂).

Example 2

Preparation of

A solution of 20.2 mmol of I′ in 80 ml of ether (prepared from 3.90 g(20.2 mmol) of I* and 12.60 ml (20.2 mmol) of a 1.6 molar n-butyllithiumsolution in diethyl ether) was added dropwise at −40° C. to a solutionof 1.92 g (10.1 mmol) of TiCl₄ in 80 ml of toluene. The reaction mixturewas subsequently allowed to warm up to room temperature over a period of6 hours and was stirred for a further 10 hours. The solution wasdecanted from the precipitated solid and the residue was washed with2×30 ml of cold (−40° C.) pentane. This gave a deep red solid.Recrystallization from toluene gave red crystals. Yield: 2.50 g (49%).Mp.: 156° C. (decomposition).

¹H-NMR (CDCl₃): δ=0.92 (d, ³J=6.5 Hz, 24H, CH—CH ₃), 2.62 (m, 4H, Cp—CH₂), 2.69 (m, 4H, N—CH ₂), 2.99 (m, 4H, CH—CH₃), 6.32-6.36 (m, 8H, Cp—H).¹H—NMR (C₆D₆): δ=0.90 (d, ³J=6.6 Hz, 24H, CH—CH ₃), 2.60 (m, 4H, Cp—CH₂), 2.93 (m, 8H, N—CH ₂, CH—CH₃), 5.76 (t, ³J=2.6 Hz, 4H, Cp—H), 6.13(t, ³J=2.7 Hz, 4H, Cp—H).

¹³C-NMR (C₆D₆): δ=21.0 (CH—CH ₃), 33.1 (Cp—CH₂), 45.6 (CH₂—N), 48.2(CH—CH₃), 114.6, 122.9 (ring—CH ═), 136.7 (ring═C—CH₂—CH₂).

MS (LSIMS) [m/e (rel. int. %)]: 503 (3) [M⁺+1H], 468 (3) [M⁺−2Cl], 114(100) [i(C₃H₇)₂NCH₂CH₂ ⁺], 65 (8) [C₅H₅ ⁺].

CHN: C₂₆H₄₄Cl₄N₂Zr(503.43). Calc.: C, 62.03; H, 8.80; N, 5.56; Found: C,61.92; H, 8.68; N, 5.43.

Cl-Analysis (Schöninger method) Calc.: 14.08; Found: 12.97.

550 mg (1.09 mmol) of this product were admixed with 15 ml ofHCl-saturated methanol solution and stirred for 30 minutes. Afterremoving the solvent under reduced pressure, a red-brown solid wasobtained. Yield: 628 mg (quantitative). Mp.: 144° C. (decomposition).

¹H-NMR (CD₃OD): δ=1.39, 1.40 (2d, ³J=6.6 Hz, 24H, CH—CH), 3.33 (m, 4H,Cp—CH ₂), 3.56 (m, 4H, N—CH ₂), 3.78 (m, 4H, CH—CH₃), 6.44 (t, ³J=2.5Hz, 4H, Cp—H), 6.74 (t, ³J=2.7 Hz, 4H, Cp—H).

¹³C-NMR (CD₃OD): δ=17.2, 18.8 (CH—CH₃), 29.2 (Cp—CH₂), 47.3 (CH₂—N),56.5 (CH—CH₃), 115.8, 125.1 (ring—CH═), 132.6 (ring—CH═), 132.6(ring═C—CH₂—CH₂).

CHN: C₂₆H₄₆Cl₄N₂Ti (576.35); Calc.: C, 54.18; H, 8.04; N, 4.86; Found:C, 53.89; H, 8.30; N, 4.72.

Cl-Analysis (Schöninger method) Calc. :24.60; Found: 26.33.

Example 3

Preparation of

A solution of 20.20 mmol of I′ in 80 ml of ether (prepared from 3.90 g(20.20 mmol) of I* and 12.60 ml (20.20 mmol) of a 1.6 molarn-butyllithium-solution in diethyl ether) was added dropwise at −40° C.to a suspension of 2.35 g (10.10 mmol) of ZrCl₄ in 80 ml of toluene. Thereaction mixture was subsequently allowed to warm up to room temperatureover a period of 4 hours and was stirred for a further 24 hours. Thesolution was decanted from the precipitated solid and the residue waswashed with 2×50 ml of cold (−40° C.) pentane. This gave a colourlesssolid. Recrystallization from toluene gave colourless crystals. Yield:3.15 g (57%). Mp.: 124° C. (decomposition).

¹H-NMR (C₆D₆): δ=0.90 (d, ³J=6.6 Hz, 24H, CH—CH ₃), 2.57 (t, ³J=6.5 Hz,4H, Cp—CH ₂), 2.82 (m, 4H, N—CH ₂), 2.90 (m, 4H, CH—CH₃), 5.77 (t,³J=2.7 Hz, 4H, Cp—H), 6.02 (t, ³J=2.7 Hz, 4H, Cp—H).

¹³C-NMR (C₆D₆): δ=21.1 (CH—CH₃), 33.0 (Cp. CH₂), 47.0 (CH₂—N), 48.6(CH—CH₃), 109.1, 113.2, 113.5, 117.1 (ring—CH═), 130.3 (ring═C—CH₂—CH₂).

MS (LSIMS) [m/e (rel. int. %)]: 544 (2) [M⁺], 114 (100)[i-(C₃H₇)₂NCH₂CH₂ ⁺], 65 (2) [C₅H₅ ⁺].

CHN: C₂₆H₄₄N₂Cl₂Zr (546.78); Calc.: C, 57.11; H, 8.11; N, 5.12; Found:C, 56.33; H 8.08; N 5.00.

Cl-Analysis (Schöninger method) Calc.: 12.96; Found: 13.57.

530 mg (0.97 mmol) of this product were admixed with 20 ml HCl-saturatedmethanol solution and stirred for 30 min. After removal of the solventunder reduced pressure, a beige solid was obtained. Yield: 600 mg(quantitative). Mp.: 188° C. (decomposition).

¹H-NMR (CD₃OD): δ=1.39, 1.41 (2d, ³J=6.6 Hz, 24H, CH—CH ₃), 3.19 (m, 4H,Cp—CH ₂), 3.46 (m, 4H, N—CH ₂), 3.78 (m, 4H, CH—CH₃), 6.45 (m, 4H,Cp—H), 6.61 (m, 4H, Cp—H).

¹³C-NMR (CD₃OD): δ=17.3, 18.9 (CH—CH₃), 28.8 (Cp—CH₂), 48.0 (CH₂—N),56.6 (CH—CH₃), 113.5, 119.7 (ring—CH═), 129.2 (ring═C—CH₂—CH₂).

CHN: C₂₆H₄₆N₂Cl₄Zr (619.70); Calc.: C, 50.39; H, 7.48N 4.52; Found: C,49.52; H 7.25; N 4.36.

Cl-Analysis (Schöninger method) Calc.: 22.88; Found:24.10.

Examples 4 to 6

Preparation of Polyethylene (PE)

The metallocene complexes I1, I2 and I3 were each suspended in tolueneat room temperature. Under an ethylene atmosphere (1 bar),methylaluminoxane (MAO) (10% strength in toluene) was then addeddropwise in each case. After 5 min, the solution slowly became turbidand warmed up as a result of the formation of polyethylene. After areaction time, the polymerization was stopped by addition of 400 ml ofmethanolic/aqueous HCl. The polyethylene was filtered off, washed withwater and acetone and dried to constant weight.

The amounts of raw materials, the reaction times and the properties ofthe polyethylenes formed are summarized in the table below.

The η-value was determined in accordance with ISO 1628-3, the weightaverage molecular weight M_(w) and the number average molecular weightM_(n) were determined by gel permeation chromatography.

TABLE Reaction Productivity Metallocene Toluene time Yield [gPE/mol × ηExample complex [ml] MAO [h] [g] c(C₂H₄) xh] [dl/g] M_(w) M_(n)M_(w)/M_(n) 4 20 mg I1 10 16 ml (26 mmol) 2 3.40 3.23 · 10⁴ 0.64 142583178 4.5 (53 μmol) 5 23 mg I2  5 12 ml (20 mmol) 4 1.50 1.00 · 10⁴ 0.7814621 3661 4.0 (40 μmol) 6 25 mg I3  5 12 ml (20 mmol) 4 0.55 0.40 · 10⁴3.48 — — — (40 μmol)

We claim:
 1. A process for preparing polymers of C₂-C₁₀ alkenes in thepresence of catalyst systems comprising as active constituents A) ametallocene complex of the general formula I

 where the substituents and indices have the following meanings: M istitanium, zirconium, hafnium, vanadium, niobium or tantalum, R¹ to R⁴are hydrogen, C₁-C₁₀-alkyl, 5- to 7-membered cycloalkyl which in turncan bear a C₁-C₁₀-alkyl as substituent, C₆-C₁₅-aryl or arylalkyl, wheretwo adjacent radicals may also together be cyclic groups having from 4to 15 carbon atoms, Si(R⁶)₃,

 where R⁶ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, R⁷ and R⁸are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, R⁹ and R¹⁰are C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, Y is nitrogen,phosphorus, arsenic, antimony, or bismuth, Z is oxygen, sulfur, seleniumor tellurium, n is an integer in the range from 0 to 10,

 where R¹¹ and R¹² are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl orC₃-C₁₀-cycloalkyl, R¹³ and R¹⁴ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl orC₃-C₁₀-cycloalkyl, n¹ is an integer in the range from 0 to 10, X¹ to X⁴are fluorine, chlorine, bromine, iodine, hydrogen, C₁-C₁₀-alkyl,C₆-C₁₅-aryl, alkylaryl having from 1 to 10 carbon atoms in the alkylradical and from 6 to 20 carbon atoms in the aryl radical, —OR¹⁵,—NR¹⁵R¹⁶ or

 where R¹⁵ and R¹⁶ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl,fluoroalkyl or fluoroaryl, each having from 1 to 10 carbon atoms in thealkyl radical and from 6 to 20 carbon atoms in the aryl radical, R¹⁷ toR²¹ are hydrogen, C₁-C₁₀-alkyl, 5- to 7-membered cycloalkyl which inturn can bear a C₁-C₁₀-alkyl as substituent, C₆-C₁₅-aryl or arylalkyl,where two adjacent radicals may also together be cyclic groups havingfrom 4 to 15 carbon atoms, Si(R²²)₃,

 where R²² is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, R²³ andR²⁴ are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, R²⁵and R²⁶ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl, n² is aninteger in the range from 0 to 10 and o, p, q, r are integers in therange from 0 to 4, where the sum o+p+g+r+1 corresponds to the valence ofM and B) a compound forming metallocenium ions.
 2. A process as claimedin claim 1, wherein M in the general formula I is titanium, zirconium orhafnium.
 3. A process as claimed in claim 1, wherein R⁵ in the generalformula I is


4. A process as claimed in claim 1, wherein R⁵ in the general formula Iis


5. A process as claimed in claim 1, wherein R¹ to R⁴ in the generalformula I are hydrogen.
 6. A process as claimed in claim 1, wherein thecompound B) forming metallocenium ions which is fused is an open-chainor cyclic aluminoxane compound of the general formula II or III

where R²⁷ is a C₁-C₄-alkyl group and m is an integer from 5 to
 30. 7. Aprocess as claimed in claim 1, wherein the C₂-C₁₀-alkene used isethylene.